With reference to FIG. 1, a motion transmission system in a bicycle 1100 comprises a chain 1101 extending between toothed wheels 1102, 1103 associated with the axle of the pedal cranks 1104 and with the hub 1105 of the rear wheel 1106. When—as in the case shown—there is an assembly of toothed wheels 1102, 1103 comprising more than one toothed wheel 1102, 1103 at at least one of the axle of the pedal cranks 1104 and the hub 1105 of the rear wheel 1106, and the motion transmission system is therefore provided with a gearshift 1110, a front derailleur 1111 and/or a rear derailleur 1112 are provided for.
In case of an electronic gearshift, each derailleur 1111, 1112 comprises a guide element 1113, 1114—also known as chain guide or cage or, in case of a rear derailleur, rocker arm—movable to displace the chain 1101 among the toothed wheels 1102, 1103 in order to change the gear ratio, and an electromechanical actuator to displace the chain guide 1113, 1114.
Each actuator in turn typically comprises a motor, typically an electric motor, coupled with the chain guide 1113, 1114 through a linkage, such as an articulated parallelogram, a rack system or a worm screw system. Typically, the electric motor is provided with a gear reduction assembly. The assembly of electric motor and gear reduction assembly is referred to hereinafter as motor gear (or geared motor). The actuator typically further comprises a sensor or transducer of the position, speed, acceleration and/or direction of rotation of the rotor of the motor, or of any moving part downstream of the rotor, down to the chain guide 1113, 1114 itself. It is worthwhile noting that slightly different terminology from that used in this context is also in use.
Control electronics changes the gear ratio automatically, for example based on one or more detected variables, such as the travel speed, the cadence of rotation of the pedal cranks, the torque applied to the pedal cranks, the slope of the travel terrain, the heart rate of the cyclist and similar, and/or the gear ratio is changed based on commands manually input by the cyclist through suitable control members, for example levers and/or buttons, typically provided on one or two manual command devices 1107 mounted to the handlebars 1108 of the bicycle 1100.
Typically, the derailleur 1111, 1112 includes a support body 1118, 1119 that is configured to be attached to the frame of bicycle 1100, and the chain guide 1113, 1114 connected to the support body 1118, 1119 by means of two connecting rods, the ends of which are articulated to the support body 1118, 1119 and to the chain guide 1113, 1114 to form said articulated parallelogram 1116.
The motor gear drives the articulated parallelogram open and closed, and as a consequence the displacement of the chain guide 1113, 1114 among the toothed wheels 1102, 1103.
In some known electronic gearshifts there is a central battery power supply unit, shared by all of the components of the gearshift 1110, and typically arranged in a fairly central position on the frame of the bicycle 1100.
In other electronic gearshifts, there is a battery power supply unit dedicated to the front derailleur (as well as one or more other battery power supply unit(s) dedicated to the other components of the gearshift). In such cases, the battery power supply unit is typically supported on the frame of the bicycle 1100 close to the support body 1118 of the front derailleur 1111, or on the support body 1118 itself of the front derailleur 1111.
Indeed, in the field of bicycle components it has always been considered that the linkage of the derailleur should move a load that is as light as possible, so as not to require particularly large sizing and high strength and, in the case of an electronic gearshift, so as to be able to use the smallest possible electric motor.
Furthermore, in the field of bicycle components it has always been considered suitable to keep electrical power consumption as low as possible in order to allow the maximum possible autonomy far from the electrical mains.
The Applicant, solving the technical problem of providing a bicycle electric front derailleur that has an alternative configuration, has now overcome these prejudices of the prior art.